Hard and super-hard materials (having micro-hardness ≥15 GPa and ≥40 GPa respectively) are required for a variety of industrial and uses such as cutting tools, wear-resistance coatings, automobile parts, abrasives, electronics, medical devices, and aerospace applications. Due to their wide range of industrial uses global demand for hard and super-hard materials has grown rapidly over the past decade. In fact, the global super-hard materials market alone is projected to reach over $20 billion by 2018. (See, “Manufacturing Activity in Developing Countries Encourages Use of Superhard Materials in Machine Tools, According to New Report by Global Industry Analysts, Inc.”, prweb.com article dated, Oct. 8, 2012.)
In response to rising demand researchers around the world have been searching for new hard and super-hard materials. The recent research in this area has focused on the exploration of compounds formed by boron (B), carbon (C), nitrogen (N), and oxygen (O), that have the potential to form strong three-dimensional covalent bonds capable of producing hard and super-hard materials. (“See, Predicting New Superhard Phases,” Journal of Superhard Materials, 2010, Vol. 32, No. 3, pp. 192-204. Allerton Press, Inc., 2010, Original Russian Text, Q. Li, H. Wang, Y. M. Ma, 2010, published in Sverkhtverdye Materialy, 2010, Vol. 32, No. 3, pp. 66-81.) With the focus on B, C, N and O containing materials, conventional metal alloys have been largely ignored as potential hard and super-hard materials due to the fact that metals and their alloys typically exhibit low hardness due to the ease with which dislocations can propagate within their structures and the type of chemical bonding typically found in such materials.
Cu33Al17 and related Cu33Al17-based alloys and composites are potentially remarkable exceptions to this rule as initial results indicate that Cu33Al17 exhibits a nanoindentation hardness of 31.4±5.8 GPa when supported on a Sn matrix, and 49.1±2.5 GPa when supported by Ag3Sn blades (“Development of Sn—Ag—Cu—X Solders for Electronic Assembly by Micro-Alloying with Aluminum,” Journal of Electronic Materials, July 2012, Volume 41, Issue 7, pp 1868-188, Adam J. Boesenberg et al.; see also, U.S. patent application Ser. No. 13/066,748.)
These hardness values are a surprising and unexpected discovery since no alloy or compound comprised solely of conventional metals has ever been reported to possess such hardness. This initial data suggests that the hardness of Cu33Al17 (and certain related Cu33Al17 alloys and composites) may be in the range of about 31-49 GPa, which is higher than both SiC, Al2O3 and on the order of TiB2. These hardness values are astounding considering the low hardness characteristics of the alloy's constituent elements (i.e. Cu and Al). As a point of reference, the Vicker's hardness of Cu is about 0.4 GPa while that of Al is on the order of 0.2 GPa. So clearly, an alloy comprised solely of Al and Cu would not be expected to have a hardness that is an order of magnitude or even several orders of magnitude greater than its component elements. As such, this discovery represents a potentially revolutionary new class of hard and super-hard metal-based materials that has a number of industrial applications and may prove to be the long sought copper based stainless steel without Fe, Cr or Ni.
It is notable that Cu33Al17 alloys (and methods for producing such) are largely absent from available scientific literature. The absence of Cu33Al17 from literature is likely due to several factors including the fact that Cu33Al17 is peritectoid compound which is not capable of being produced using conventional solidification techniques (i.e. will not produce a homogenous, uniform composition with the intended stoichiometry). Similarly, the inventors discovered that long term annealing also fails to produce the desired phase since the diffusion kinetics are sluggish. The difficulties associated with creating Cu33Al17 in bulk form initially led the inventors to believe that solid-state mechanical alloying of either Cu and Al powders or Cu—Al alloy powders would be the only way to create single-phase, homogenous Cu33Al17. Surprisingly, the inventors discovered a new method for creating such materials that does not require the complexity and expense of mechanical alloying.
Prior to the current discovery, the only known reference to Cu33Al17 was its identification as a potential phase within of a larger Cu—Al peritect diagram (See, Murray J. L., Al—Cu (Aluminum-Copper), Binary Alloy Phase Diagrams, II Ed., Ed. T. B. Massalski, Vol. 1, 1990, p. 141-143.) Although more recent Cu—Al phase diagram references have been reported, the Murray reference serves well to indicate the temperatures and composition of this Cu33Al17 phase. While Murray identifies Cu33Al17 as potential phase, it is important to note that there is no known prior reporting of a homogenous and uniform Cu33Al17 alloy in bulk form or a method of making the same.
These and other objects, aspects, and advantages of the present disclosure will become better understood with reference to the accompanying description and claims.